Grant: Operating Grant

The voltage insensitive KCa3.1 channel is a membrane protein that forms a pore in the cell membrane through which K+ ions diffuse down their electrochemical gradient. The channel is activated by internal Ca2+ so that its activity varies in response to a variety of chemical (hormones, neurotransmitters) and physical (shear stress) external stimuli. Channel activity is also controlled through intracellular chemical modifications involving several protein kinases including AMPK which is sensitive to the cell energy status. Recent studies have demonstrated that the activation of KCa3.1 constitutes an obligatory step in the control of vascular tone by the endothelial cells which are expressed at the internal surface of blood vessels. This channel is also documented to be involved in the proliferation of vascular smooth muscle cells in pathological conditions. As a result, KCa3.1 is now emerging as a therapeutic target for cardiovascular disorders such as atherosclerosis, restenosis after angioplasty and traumatic-induced edema. In the proposed research program we intend, using electrophysiological measurements, computer-based modeling and tools from molecular biology, 1) to identify the amino acids which are responsible for controlling the K+ ion flow through the channel pore, and 2) to determine how the structural changes induced by the binding of Ca2+ to the channel are conveyed to the amino acid responsible for channel opening. The preliminary results we obtained to date indicate in this regard that a region of the channel referred to as the selectivity filter plays a crucial role in the Ca2+ dependent control of K+ ions flow and represents an important binding site for KCa3.1 potentiators and inhibitors. This information is essential to understand the mechanisms by which pharmacological agents known to affect KCa3.1 activity exert their action, while constituting an essential step to design molecules capable of either stimulate or block KCa3.1 activity.